Ftnesses



(No Model.)

0. F. SCOTT. MEANS FOR GOMPBNSATING FOR TEMPERATURE RESISTANCE CHANGES. No. 606,033. Patented June 21,1898.

ITNESSES: INVENTOR- UNTTan STaTijs PATENT Curries.

CHARLES E. SCOTT, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO THE VESTINGIIOUSE ELECTRIC AND MANUFACTURING COMPANY, OF

SAME PLACE.

MEANS FOR COMPENSATING FOR TEMPERATURE-RESISTANCE CHANGES.

srnoirroarr'err forming partof Letters Patent No. 606,033, dated June 21, 1898.

I Application filed January 21, 1895. Serial No. 536,666. (No model.)

(Case No. 629,) of which the following is a specification.

My invention relates to electric induction apparatus, and more particularly to electrical indicating and measuring instruments employed in connection with systems of distribution for alternating currentssuch, for example, as is shown in the patent granted to O. B. Shallcnberger January 1, 1895, No. 531,868; and it has for its object to provide a means whereby variations in the resistance of certain parts of such apparatus due to variations in temperature maybe compensated for and the movements of the indicating or registering device be thus caused to indicate or register correctly irrespective of any changes in temperature.

It is well known that'tne resistance of metallic conductors to the passage of electric currents increases as their temperature rises and that such changes in resistance vary widely in different metals. In certain electrical indicating and measuring instrumentssuch, for example, as that shown in the patent to O. B. Shallenberger above referred toit is therefore necessary either to construct the shunt-circuit and the armature of metals having such temperature-resistance coefficients that the changes in resistance due to changes in temperature will be so small as to be practically negligible, or to supply some means for compensating for the changes in resistance due to changes in temperature in order that the amount or degree of movement of the armature may be such as to correctly indicate the energy transmitted over the line.

It is the purpose of my present invention to overcome the difficulty by the method of compensation, and to this endIpropose to so construct the shunt-circuit that its action upon the armature will increase with the rise in temperature in the same degree that the l conductivity of the armature decreases. For

the purpose of effecting this result I propose to employ two shun t-circuits having different resistance values and different temperatureresistanoe coefficients and to so place them with reference to the armature that they will act differentially upon it.

Referring to the drawings, Figure 1 is a diagram illustrative of my invention as applied to a two-phase system of distribution and an indicating-wattmeter therefor. Fig. 2 is a similar view showing a modified arrangement of circuits.

Referring now in detail to Fig. 1 of the drawings, 1 is a two-phase generator, and 2, 3,,

separately connected in shunt upon circuit 4:

5, these coils being so placed with reference to the armature 7 as to act differentially thereon. In series with one of these coils as, for example, the coil 10I place a non-inductive resistance 12, constructed of metal having a relatively low temperature-resistance coefticient-such, for instance, as German silver-and in series with the coil 11 I place a non-ind uctive resistance 13 of greater value than the resistance 12 and constructed of a material having a relatively high temperature-resistance coefficient-such, for instance, as copper.

The metals above named are merely given as examples of suitable metals to be employed, and I do not wish it to be understood that my invention is restricted to any particular conducting materials, it being essential merely that the two resistances should have different degrees of conductivity at the same temperature, whatever that may be, and that the temperature-resistance coefficients of the two shall be different.

The modification of my invention illus- 2 scenes trated in Fig. 2 of the drawings dillfers from that shown in Fig. 1 only in the relative arrangement of the shunt-connected circuits. in this modilication, instead of providing two separate coils so located as to act dillferentially upon the dish, 1 wind the two cond uctors together into a single coil 11-, and thus get the desired dillerential action.

In order that the operation of my invention may be clearly understood, let us suppose that the resistance 12, of German silver, has a value of one hundred and the resistance 18, of copper, a value of two hundred, and that the teinperature-resistancc coellicient of the former is such that for a certain change in temperature the increase of resistance is one per cent, and that for the same change in temperature the increase of resistance in the latter is ten per cent. It follows, therefore, that the resistances at the said higher temperatu re will have values of one hundred and one and two hund red and twenty,respectively, and. that the currents through the shunt-circuits will he reduced one per cent. and ten per cent, respectively. if we represent the current in the first circuit at the first temperature as one and in the second circuits as .50, at the same temperature, it follows that at the higher temperature the currents will be approximately .99 and .-l5 in the respective circuits. If now the currents in the two circuits be made to act dillierentially upon the armature as indicated, the resultant effect will he one minus .50, or .50 at the first temperature, and .95) minus 01-5, or 5i at the higher temperature, or an increase in the resultant action upon the armature ol .O-i at the higher temperature over that at the lower. It will thus be seen that the resistances may he so proportioned and the n'iaterials employed therefor be so selected that the increased resultant effect of the shunt-connected circuits upon the armature maybe made to exactly coinpensate for the loss in conductivity in the latter by reason of such increase in temperature.

The proportions used in the above illustration will. give very fair compensation if the disk 7 be of aluminium.

While I have illustrated and described my invention as applicable to and primarily intended lorusc inconnectionwitheleetricalindicating and n'icasuring instrnmen ts, I desire it to be distinctly understood that it in applicable to any and all forms elf electrical apparatus .in which a compensation for changes in resistance due to changes in temperature is necessary or desirable.

I claim as my invention 1. In an indicating instrument for alternating currents, the comhiiiiatiou with the retatable closedcireuit armature of two actuating-circuits in inductive relation to said armature and containing nondinluctlve rcsistances, one of which has a 'reater value and a higher teinperatiu'e-r s1 ance cool? ficient than the other, substantially as dw scribed.

23. The combination with a movable armature, of shunt and series connected circuits in inductive relation thereto and non-i nd netive resistances olf different values in the respective sluint-circuits and one of which has a different temporature-resistance coel'liciont from the other.

3. The combination with a movable armature, ofseries and shunt connected actuating coils therefor and a i'lon-iinluctivo resistance in series with each of said shuntcrmnected coils one of which has a greater temperaturercsistance coellicient than the other, substantially as dcscribel'l.

-.l-. In an electrical indicating or measuring instrument, a movable armature, sericsconnected coils upon one side of said z'u'mnturr,

and sluuit-connectcd coils upon the other side o thereof, a resistance having a relatively small temperature-resistance coel'licient in series with one of the shunt-coils and a greater resistance having a relatively large tempera ture-resistance coel'licient in series with the other shunt-coil, substzmtially as desm-ibed. in testimony whereof l have hereunto su bscribed my name this lltlth day of January, A. D. 1895.

(ll littti. l W l )T'I. \Vitnesses:

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